The invention concerns a solenoid valve of the kind mentioned in the preamble of claim 1.
In such solenoid valves the closing member is normally integrated in the armature, being a sealing surface inserted in the armature, which, by means of an armature return spring, at currentless (non-magnetised) coil is brought to sealingly bearing against the valve seat, and at magnetised coil is pulled away from the valve seat to permit medium flow through the valve opening. Such a solenoid valve, in which the medium flow is interrupted at currentless coil, is called a normally closed (N.C.) valve. In certain applications it would be advantageous to use a normally open (N.O.) valve, whose construction, however, is usually of a much more complicated nature.
The most frequently used medium flow direction in normal valves of the embodiment described above is into the valve housing, past the closing member and out through the valve opening in the valve seat. This gives a secure closing function, the increasing differential pressure acting upon the closing member to pressing harder against the valve seat. If, however, the flow direction is reversed, it is achieved that if the differential pressure exceeds a certain value, which is determined by the valve opening area and the force influence of the return mechanism, the pressure will move the closing member away from the valve seat and let the medium flow through the valve. In certain cases this function can be desirable as security valve function, but the pressure at which the valve opens is substantially determined in advance by the dimensioning requirements for return mechanism and valve opening determined by the solenoid valve function.